1. Field of the Invention
The present invention relates generally to systems and methods for converting a measurement into engineering units. More particularly, the present invention relates to systems and methods for employing fast techniques of converting analog measurements to engineering units.
2. Related Art
A. General
Many devices depend on measuring a physical quantity, such as temperature or torque, and converting this quantity into a known engineering unit, such as Fahrenheit or Foot Pounds.
Typically, a first step in a conversion process is a transducer. In a typical application, the transducer changes a physical quantity, such as temperature or torque, into a linear or nonlinear proportional voltage. This value is known as an analog voltage that can have any value within a given range.
The transducer is normally interfaced with an analog-to-digital converter, which changes the analog voltage to a digital voltage. The digital voltage can then be expressed as a digital representation of the analog voltage.
In order to be valuable to a user for analysis, most measurements of physical quantities must appear in an engineering units format. Thus, after the analog-to-digital conversion, the resulting data must be converted from a digital value into an engineering unit format. This conversion process, termed engineering unit conversion, is accomplished by interfacing the analog-to-digital converter to a data-acquisition system, which gathers all digital data coming from the analog-to-digital converter. The data acquisition system then applies data to a stored program involving software. The data is then completely evaluated in software by a mathematical equation.
However, these mathematical equations often involve complex polynomial equations increasing computation time and complexity of the data acquisition system. At higher rates of conversion, it becomes impractical to convert voltage measurements of physical quantities, into engineering units. For instance, in a system in which events are represented or acted upon as they occur--"real time"--it is impractical to convert a voltage measurement into engineering units using the above technique of evaluating mathematical formulas at the time of measurement. In such cases, the measurement rate may exceed the ability of the measurement hardware to convert into engineering units. Therefore, measurement quantities are usually recorded in their voltage format, then converted later during a separate data analysis phase.
What is needed is a system and method that obtains engineering units in "real time". In other words, there is a need for a data acquisition device that can perform the entire data gathering process, as well as, the conversion process in "real time."
It is presently possible to perform this conversion in "real time" utilizing very high speed computing devices. However, the cost of employing such devices is prohibitive. Therefore, there is also a need for a device that can perform "real time" conversion at a dramatically smaller cost than is presently possible.
B. Thermocouples
One application of the conversion process mentioned above, involves measuring temperature via a thermocouple device. Thermocouples utilize two dissimilar wires bonded together that are applied to a point where a temperature is to be measured. A temperature gradient along those wires causes a thermoelectric effect generating a voltage across the two wires. This voltage may then be applied to an analog-to-digital converter and then data acquisition conversion devices, as discussed above, resulting in an engineering unit, e.g., Fahrenheit. A problem associated with thermocouples is connecting them to a converting device at some intermediate junction with other possibly dissimilar wires. This intermediate junction creates unwanted voltages along these wires due to dissimilar metals and temperatures between the thermocouple device and the converting device. The increased or decreased voltage is thereby transferred to the conversion device, which produces an inaccurate temperature unit reading.
What is needed is a device that obtains engineering units in "real time" and is simultaneously able to compensate for the thermoelectric effect of intermediate wiring junctions relating to thermocouples.